This invention relates to a method of simulation of a digital logic circuit.
The simulation of a digital logic circuit has in the past been effected by a general-purpose computer in software fashion. Examples of such logic simulation are disclosed in the literatures listed below:
(a) "Exclusive simulation of activity in digital networks" by Ernst G. Ulrich, February 1969, Communications of the ACM, Vol. 12, No. 2, pp. 102 to 110; and PA1 (b) "Digital Logic Simulation In a Time-Based, Table-Driven Environment Part 1, Design Verification" by S. A. Szygenda and E. W. Thomson, March 1975, Computer, Vol. 8, No. 3, pp. 24 to 36.
The logic simulation is effected by forming a logic simulation circuit or simulation model in software fashion. In simulating a logic circuit L comprising an integrated circuit IC as shown in FIG. 1, for instance, a logic circuit equivalent to the integrated circuit IC is formed by the use of an AND gate, an OR gate and other basic circuits in software fashion. In this manner an output in response to an input stimulus for the AND and OR gates is calculated. Although this technique is quite useful, there are certain problems. For example, in the event that it is impossible to replace an integrated circuit making up a component element of a logic circuit by an equivalent logic circuit comprising such basic circuits as an AND gate and an OR gate, it is impossible to form a simulation circuit or simulation model for such a logic circuit. Therefore the logic simulation is impossible or, at least, unsatisfactory. In particular, in the case of microprocessors presently available on the market which have a very high degree of integration (and to which the internal logic circuit diagrams are not generally made public), it is very difficult to obtain an equivalent logic circuit utilizing simply an AND gate and an OR gate. As a result, the logic simulation of a logic circuit using a microprocessor is far from complete. An example of a prior art attempt at simulation of a microprocessor is disclosed in "Chip-Level Simulation of Microprocessors" by James R. Armstrong and Garry W. Woodruss, January 1980, Computer, Vol. 13, No. 1 pp. 94 to 100.
In addition to the abovementioned problem, if the logic circuit is complicated, logic simulation by use of a general-purpose computer requires a very long time for the computer processing necessary for logic simulation. This tends to be the case even when the computer program instructions for computation of an output in response to an input stimulus of the basic circuits such as AND and OR gates are executed at a very high speed.